Putnam County emergency management director Frank Chapman said the explosion involved about 50 tanks of acetylene that were at Airgas awaiting refilling. What caused the tanks to explode is now under investigation.

Chad Jones, a firefighter with the Bancroft Volunteer Fire Department, said four cylinders continued to burn Monday evening and that crews were letting them burn out. They were dousing other tanks with water to keep them from exploding, said Jones.

The company was storing the tanks in a bay behind the facility. Jones said after the first tank exploded, “it was like a chain reaction,” with fireballs shooting 100 to 150 feet in the air. A nearby business evacuated, and windows shattered in the back of the Airgas plant, Jones said.

Doug Barker, chief financial officer at nearby Clark Truck Parts, said “we felt our building shake like it’s never come close to shaking before from a storm or anything. It was enough to make us run.”

Barker said he and another company official bolted from their offices, and he ran to the road and saw dark smoke in the air. Soon afterward, they heard several smaller explosions and saw fire, he said.